It has now been recognized that the world's environment is suffering too much from global warming caused by greenhouse gas exposure in the atmosphere. To address this problem governments are now starting to adopt targets for reducing the emission of greenhouse gases to the environment and play their part to address this problem for future generations. While some countries have not adopted a firm goal, other countries, for example Australia, have adopted a policy for the reducing greenhouse gases by 20% by the year 2020.
Greenhouse gases can be emitted from cars, industry, farming, and households to name a few. While certainly not as apparent as a large factory with tall smokestacks, within a normal household the gas burning appliances, such as furnaces, water heaters, etc., all release such greenhouse gases as a by-product of the combustion process itself. While the appliance industry has taken a leading role in energy efficiency and environmental concern, further improvement is always foremost in mind of the appliance design engineer.
With such further improvement in mind, especially with the increased awareness of global climate change and changing governmental regulations, it is noted that hot water heaters can be one of the more fairly inefficient appliances in energy conservation, and therefore require the burning of additional fuel or the converting of more electricity to heat to maintain the set point temperature. This, of course, results in the additional production of greenhouse gas directly from the appliance beyond that which a more efficient appliance would produce.
Recognizing the issue of greenhouse gas, many consumers have moved from gas burning appliances to electric appliances. A typical electric water heater includes one or two electric heating elements to heat water within a water holding tank. Particularly, when the water within the holding tank drops below a predetermined temperature, there is a call for heat and the heating elements are energized to raise the temperature of the water. Once the temperature of the water is raised to a predetermined or user determined set temperature the heating elements are deactivated.
Typically, in water heaters having two heating elements, the heating elements are spaced vertically apart from one another. Further, when there is a call for heat, the heating elements can be controlled by a controller such that they can be energized simultaneously, or independent of one another to provide the most efficient heating of the water, depending on operating conditions and inputs by the operator.
To determine the temperature of the water within the holding tank, the water heaters include temperature sensors. Typically, a temperature sensor is placed above and proximate to each heating element. Thus, the individual temperature sensors can determine the localized temperature of the water proximate the individual heating elements. This allows for localized heating of the water in the water heater to, again, improve efficiency.
In addition to the movement from gas burning to electric appliances, many consumers have installed alternative energy sources of electricity, such as wind turbines, solar panels, etc. to further reduce the production of greenhouse gases. While such alternative energy sources can have a great impact in this regard, their availability and capacity can be limited compared to electric power from the grid. Unfortunately, current appliances are not designed in any way to recognize this limitation, and instead continue to operate as if the availability of electric power is limitless.
What is needed are appliances, appliance controllers, and methods of operating such appliances to take into consideration the availability and capacity of alternative energy sources so that additional efficiencies can be had. The invention provides such appliances, appliance controllers, and methods of operating such appliances. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the embodiments of the present invention provided herein.